For words that have only 3 letters, there is absolutely no 4th letter. By way of example with the word “include”, there are no far more letters Later on and therefore must be the word "increase". The word “addict” is inside the BIP39 wordlist but you would've made use of https://sociallawy.com/story9133436/the-5-second-trick-for-ledger-seed-phrase-bip39